Bare floors in commercial and industrial buildings are commonly cleaned with floor scrubbing machines. Such machines apply a scrubbing solution of water and detergent to the floor, agitate it with one or more rotating tools such as scrub brushes or pads to loosen soilage on the floor and suspend it in the solution, then pick up the soiled solution with a vacuum pickup squeegee located behind the brush or brushes.
The pickup squeegee is a critical part of such a floor scrubbing machine, and has been the object of extensive design development over the years. It extends transversely across the machine behind the brushes, and comprises a rigid squeegee frame having generally an inverted U-shaped cross section. Two rubber-like lips or blades are attached to this frame, one to each of its vertical legs, and extend down below the frame to the floor across the total width of the squeegee. An opening in the top center of the frame connects to a suction hose through which vacuum sucks soiled scrubbing solution from the space between the blades to a recovery tank. The entire assembly is attached to the machine with a hinged linkage that allows the squeegee blades to conform to irregularities in the floor surface and maintain a full contact with the floor.
As the machine travels in its normal forward direction, the forward squeegee blade meets the soiled scrubbing solution standing on the floor behind the brushes or other scrubbing tools. There are notches or other openings along the lower edge of this blade which allow the solution and some air to pass through the blade into the vacuumized space between the blades, from where it is sucked into the recovery tank. The rear squeegee blade is under enough down pressure to flex it back somewhat and give it a continuous contact along its length with the floor. It serves as a wiper lip to keep the scrubbing solution from escaping out of the squeegee chamber and to wipe the floor as dry as possible. Commonly this will be a damp dry condition which is dry enough so it is not slippery to walk on, and which will dry completely in a few minutes.
Common practice in floor scrubbing is to drive the machine the length of the area to be scrubbed, make a sharp 180 degree turn, drive back parallel to and slightly overlapping the first pass, and continue thus until the entire area is scrubbed. For the most part this procedure works well, but it also has a problem. As the machine is turned sharply at the end of each pass the squeegee moves in a largely sidewise direction, with the result that some of the soiled solution on the floor in front of the squeegee flows sidewise along the front surface of the front squeegee blade and escapes beyond the end of the squeegee which is on the inside of the turn. This leaves an unsightly and possibly hazardous puddle on the floor at each end of each pass.
The easiest way to control this is to make the turn, back up the scrubber across the resulting puddle until the puddle is in front of the squeegee, and then drive forward. The squeegee will pick up the puddle, and normal scrubbing can continue.
However, such a reverse direction maneuver puts additional demands on the squeegee. In forward travel the rear squeegee blade acts as a wiper, and for that purpose it has a continuous bottom edge. In reverse travel, however, this blade becomes the leading blade, and it should allow water to pass under it. But a blade with a continuous bottom edge will wipe water ahead of it in reverse as well as in forward travel, and not pass it through. So in some cases this blade has been modified to serve the function of passing water under it in reverse while still wiping cleanly in forward travel.
One common modification has been to make a series of vertical grooves in the trailing surface of the trailing lip. This construction has been used in a number of floor scrubbers and is shown, for example, in U.S. Pat. No. 4,817,233 (col. 4, li. 45-54). In reverse travel the flexing of the lip edge contacting the floor brings these grooves in contact with the floor, and water can pass through them to the interior cavity of the squeegee. The leading surface of the lip is left smooth, and the corner where the leading surface intersects the bottom surface remains as a contact line with the floor, to provide wiping action in forward travel.
In practice, however, there has been a problem. The bottom of each groove creates a thin section in the bottom surface of the squeegee blade, and these thin sections are not as stiff as the full thickness material between the grooves. Consequently, in forward travel these thinner sections do not press against the floor as firmly as the adjoining thicker sections. The result is that in forward travel these wiping squeegee blades leave a series of water streaks on the floor behind the squeegee corresponding to the grooves in the blade. These water streaks increase the hazard of a pedestrian slipping on the floor before it dries, and sometimes remain visible as dried muddy streaks after the floor dries. As might be expected, such shortcomings are objectionable to building managers where the equipment is used.
One effort at correcting this deficiency has been to make the squeegee blade thicker, so that the material at the bottoms of the grooves is as thick as a normal ungrooved blade. In this approach the space between the grooves also becomes thicker, so that in effect one has a normal thickness blade with a series of ribs on its back surface. These ribs act as stiffeners, and a blade made in this way does not flex as readily as a normal squeegee blade. But a squeegee blade must flex to be an effective wiper, so to get that flexing a greater than normal down force must be applied. This produces extra frictional force at the floor, which translates into harder pushing in a hand pushed machine, or higher power demand from the traction motor and batteries in a self propelled machine, with attendant reduced run time per battery charge. Also, the wear life of the squeegee blade is shortened. For these reasons this design has not been entirely satisfactory.
Because of the above shortcomings in prior art squeegee wiper blades there is an unfilled need for a squeegee blade that will flex without undue down pressure, will wipe cleanly without streaking in forward travel and will allow water to pass under or through it in reverse travel.